recently bought a pup was told he was 10 weeks old and had his jabs already due to being bred on a farm but they didnt have the papers to prove it, all sounded abit dodgy so weve decided to get him done again he's had his first jab now and the vet recommended taking him for walks in the countryside and socialising him as much as possible, i have been driving to a racecourse and walking him in the fields there meeting alot of dogs most who seem to have responsible owners it may be too late now but is this dangerous for my pup and wats the risk factor of him getting anything from it? many thanks.

If you think he only had his first injection, then yes all means take him out as you already done but carry him. You don't want put him at  risk of him picking up something while he's out. especially where dogs walk. Once he's had his second injection vets said when can go for walks the I personally breath safe then. Good Luck.